Study on Isolation and Raman Spectroscopy of Glycinin in Soybean Protein

Abstract

The secondary structures of soybean glycinin was investigated by Raman spectroscopy and its acidic and basic polypeptides were isolated. The results showed that the secondary structures of glycinin were mainly composed of 21.51% α-helix, 41.62% β-sheet, 24.70% β-turn, and 12.18% random coil. For the disulfide bridge (—S—S—), the ratios were 34.8% gauche—gauche—gauche (g—g—g), 32.1% gauche—gauche—trans (g—g—t), and 33.1% trans-gauche-trans (t—g—t). The I850/I830 intensity ratio of glycinin Raman tyrosine doublet confirmed that the contents of the N-buried and N-exposed tyrosine residue were 14.1% and 85.9%, respectively. The typical acidic subunit A and basic subunit B were clearly separated by heat denaturation and reduction with β-mercaptoethanol, and their corresponding molecular masses were 42 and 38 ku, respectively. Raman spectroscopic analysis can be used to determine the secondary structural properties of glycinin. Further studies of the glycinin structures will be helpful for the utilization of soybean protein resources.Supported by Grain & Corn Engineering Technology Research Center, State Administration of Grain (GA2017004), Science and Technology Research Project of Henan (172102110205). Keywords:: Soybean glycinin, Secondary structures, Raman spectroscopy, Acidic and basic polypeptides